Well logging systems and methods have been devised which employ downhole controllers or microprocessors disposed within the logging sonde under surface system control for purposes of data acquisition, telemetry, and control, a representative one of which is described in United Kingdom Pat. No. 1,597,627 to Belaigues, et al., filed Jan. 26, 1978 and entitled "Data Transmission System for Borehole Exploration Apparatus".
One reason for the need for such complex systems has been the correlative desire to measure an increasingly larger variety and number of complex parameter data in a given traversal of the logging sonde through the borehole--a trend occasioned by the modern practice of combining an increasingly larger number of logging tools in the same "tool string". Thus, with such vast amounts of data being derived in modern logging operations, it became evident that some manner of computerized control was essential.
However, one problem with such prior computerized systems and methods has been their relative inflexibility caused by numerous factors. One approach has been to hard-wire various tool interfaces and system controllers in a custom manner for each tool under consideration. This resulted in the unfortunate situation wherein some tools were thus not adapted for use in conjunction with other tools without time consuming and expensive hardware modifications prior to the logging operation.
This in particular meant that prior to commencing a logging operation and even more so after such an operation had begun, there was no simple way to modify the order in which various tools comprising the tool string were interrogated by the downhole controller. Moreover, and in like manner, there was no way to vary the number of functions requested by the downhole controller from a particular tool or the order in which they would be supplied, as this decision had been preordained by the way the various downhole interfaces, system controller, and controllers associated with each tool had been set up.
This, in turn, frequently meant that extremely valuable logging cable band width was being occupied or, more accurately, cluttered with some types of information as temperature data, power supply voltages, borehole widths, and the like which were simply not needed as frequently as were other classes of data.
With prior systems it was impractical to vary the combinations of parameters being measured during the logging operation in acordance with varying depth increments over which they may be desired. For example, some parameters only needed to be monitored every four feet of borehole whereas others were monitored every 1/64 foot. Thus, data required every four feet would nevertheless be derived and transmitted to the surface every 1/64 foot. The only way to solve this problem appeared to be to reduce logging speeds to insure that the more important data was obtained at each borehole elevation of interest prior to moving to the next depth level--a "solution" which is extremely impractical from a commercial standpoint.
These and other disadvantages and problems of the prior art are overcome by the present invention, and an extremely flexible and adaptable well logging data acquisition, telemetry, and control system and method have thus been herein provided.